Magnesium base alloys



Patented 1933 UNITED STATES PATENT OFFICE.

nonnnr 'r. woon,

OF LAKEWOOD, OHIO, ASSIGNO R, IBY .H'ESNE ASSIGNIENTS, 1'0

IAGNESIUI men annoys 80 Drawing.

The invention relates to magnesium base alloys. Heretofore, these alloys have contained as essential alloying elements such metals as aluminum, copper, and cadmium. So far as I am aware, no one has heretofore produced or investigated alloys containing magnesium in large amount and smaller, but effective, amounts of zinc, tin, and calcium, in which manganese may also be a valuable. alloying element.

I have discovered that magnesiumbase alloys containing tin, zinc, and calcium with or without manganese ma be cast, rolled, forged, extruded, and similarly treated according to well known methods provided the proper proportions of each alloying element be present as hereinafter disclosed. They are also susceptible of improvement by the ordinary heat treatments known to the art, and in addition, the physical properties, especially the yield point and hardness, of these alloys may be substantially improved by so-called artificial aging treatment subsequent to the usual elevated temperature heat treatments. I have dis- 4 covered that useful alloys of this nature may be compounded containing from about 0.1 per cent to about 20 per cent tin, from about 0.1 per cent to about 10 per cent zinc, and from about 0.05 per cent to about 2.0 per cent calcium. If manganese be added in amount from about 0.1 per cent to about 2.5 per cent, the hardness and other beneficial properties of the alloy are also increased.

The particular composition of each constituent to be chosen depends upon the use to which the alloy is to be put. Considering, for instance, the constituent zinc, if the alloy be intended for casting purposes, an amount of from about 2 percent to about 6 per cent is suitable, and I prefer to use about 4 per cent whereas for purposes of extrusion from about 0.1 per cent to about 10 per cent of zinc may be advantageously addedto the alloy. If an alloy for forging or rolling is desired, the zinc is preferably present in amount not less than about 0.1.

per cent and not greater than about 1.0 per cent.

Application filed lay 1a, 1931. Serial rm. saaeo'z.

- strength The element tin may be incorporated in the alloy in amounts from about 4 per cent to about 8 per cent for casting purposes, and for forgings or for extrusion purposes in amounts from about 0.1 per cent to about 20.0 per cent, although I prefer to add tin in amounts between 4 per cent and 12 per cent.

The element calcium should for casting purposes, be preferably kept below about 0.5 per cent but may be used in amounts from about 0.1 per centte 2 per cent in forged or extruded products.

' If the element manganese be added as a hardener, it should, .in casting alloys, be preferably lower than 1 per cent, from 0.1 per cent to about 2.5 per cent can be used in alloys 'to be forged or extruded.

lVIy'new alloys may be made up according to the usual metallur ical methods of alloying but I prefer to a d the tin and manalthough a ganese to the molten magnesium in the form of an alloy of tin and manganese suitably proportioned in metal content to give the desired final ratio of tin and zinc in the alloys. The calcium may be added in the form of pure calcium. The zinc may be added either separately or as a tin-zinc rich alloy. The magnesium, tin, zinc, calcium, and manganese from which the alloys are made may or may not.contain impurities,

resistance to corrobase As an illustration of the lncrease 1n yieldi, e o

point to which alloys within the see my invention are inherently suscepti have made up an alloy containing a per cent tin, about 3 per cent zinc, about 0.73 per cent manganese, and about 0.25 per cent calcium and cast test specimens in sand molds. After casting, the yield point was 8,800 pounds per square inch, the tensile 23,900 pounds per square inch, and

Such allo s as are herein dis bout -5 artificial aging of 24.-

the Brinell hardness 44.. After a solution treatment of 24 hours at 500 centi ade followed by an aging treatment of24 ours at 150 centigrade, the yield point was 18,200 pounds per s uare inch, the tensile strengt 31,900 poun the Brinell hardness 56.

increase in yield point similarl phenomenal in nature, although numerica ly not so great, is observable if the alloys be artificially aged after casting and without preliminary heat treatment at an elevated tema sand cast alloy perature. For instance, containing 5.4 per cent tin, 4.55 per cent zinc,.0.72 per cent manganese, and 0.25 er cent calcium in the as-cast condition had a yield point of 9,910 pounds per square inch and,a Brinell hardness of 44, and after an.

hours at 150 centigrade, it had a yield point of 14,550 pounds per square inch and a hardness of 57.

sand cast magnesium base alloy containing about 5 per cent tin, 5 per cent zinc, and 0.25 per cent calcium was tested in the as-cast condition and had a yield point of 10,200 pounds per square inch, a tensile strength of 22,600 pounds per square inch, an elongation of 4.? per cent in 2 inches, and a Brinell hardness of 326.

A sand cast-magnesium base alloy containing about 5 per cent tin, about 4- cent zinc, and about 0.25 per cent calcium in the as-cast condition had a yield point of 9,450 pounds per square inch, a tensile strength of 22,640 pounds per square inch, an elongation of 5.5 per cent in 2 inches, and a Brinell hardness of 45. After heat treatment of hours at 550 centigrade, it had a yield point of 0,050 pounds per square 1110b, a tensile strength of 29,030 pounds per square inch, an elongation of 0.2 per cent in 2 inches, and a Brinell hardness of l5. Specimens thus heat treated were, in addition, aged 24 hours at 150 centigrade and had a yield point of 19,240 pounds persquare web, a tensile strength of 32,230 pounds per square inch, an elongation of 3.7 per cent in 2 inches, and a'Brinell hardness of 59. On heat treatment and artificial aging, there is apparent an increase in yield point of almost 10,000 pounds per square inch, an increase in strength of almost 10,000 pounds per square inch, and an increase in hardness of over 144 Brinell num- In the worked condition, alloys within the scope of this nvention have exceptionally good physical properties. For instance, an extrudedmagnesium base alloy containing about 4 per cent tin, 3 per cent zinc, 0.2 per cent calcium, and 2.5 'per cent manganese. had a yieldpoint of 26,000 unds per square inch, a tensile strengtho 46,000 pounds per square inch, and an elon ation of 13 .5 per cent in 2 inches. Similar an s per square inch, andtion of 10 per cent in 2 extruded magnesium about 8 per cent tin, per cent calcium, and 1 er cent manganese had a yield point of 9. out 27,300 pounds per square inch, a tensile strength of about 45,000 pounds per square inch, an elongainches, and a Brinell base alloy containing 3 per cent zinc, 0.2

hardness of 66. Y

The heat treatment which I have found especially suited to these alloys consists in a preliminary treatment for a number of hours, preferably from 4 to 16, at about 450 centigrade to 560 centigrade followed by an artificial agin for a number of hours, preferably from a out 4 to 24, below 200 centigrade and preferably between about 150 centigrade to 200 centigrade. Increase in aging time usually results in increase in yield point and hardness.

In the specification and the appended claims, the term magnesium base alloy denotes an alloy containing more than per cent magnesium, which metal may be either of high purity or may contain the usual impurities found in commercial magnesium. Y

I claim:

1. An alloy consisting of about 2 to 6 percent of zinc, about a to 8 per cent of tin, about 0.05 to 2 per cent of calcium, the balance being substantially magnesium.

2. An alloy consisting of about 0.1 to 20 per cent of tin, about 0.1 to 10 per cent of zinc, about 0.05 to about 2 per cent 01" caloium, the remainder being substantially magnesium.

3, An alloy consisting of about 0.1 per cent to 20 per cent of tin, about 0.1 per cent to 10 per cent of zinc, and about 0.05 per cent to 2.0 per cent of calcium the balance being substantially magnesz' 1m, characberized by high hardness and. yield point and having an internal structure produced by a heat treatment of i to 16 hours at 450 centigrade to 560 centigrade followed by further aging treatment at a temperature less than 200 centigradc.

RBERT T. WOOD. 

